function objToSearchString(obj){
    var str =''
    for(key in obj){
        str+=`${key}=${obj[ket]}&`
    }
    return str.slice(0,str.length-1)
}

function ajax(method,url,params){
    return new Promise((resolve,reject)=>{
        var xhr =new XMLHttpRequest()

        xhr.open(method,method =='get' ? url + "?"+objToSearchString(params):url )

        xhr.onreadystatechange=function(){
            if(xhr.readyState == 4   ){
                resolve( JSON.parse(xhr.responseText))
            }
        }
        xhr.setRequestHeader('content-type','application/x-www-form-urlencoded')
        xhr.send(method == 'get'? null:objToSearchString(params))
    })
}